Automatic visual inspection of centering marks engraved on ophthalmic lenses

Xavier Fernandez; Salvador Bosch

doi:10.1117/12.196113

23 November 1994 Automatic visual inspection of centering marks engraved on ophthalmic lenses

Xavier Fernandez, Salvador Bosch

Proceedings Volume 2249, Automated 3D and 2D Vision; (1994) https://doi.org/10.1117/12.196113
Event: Optics for Productivity in Manufacturing, 1994, Frankfurt, Germany

Abstract

We present a complete procedure for automated inspection of engraved marks and ink marks placed on ophthalmic lenses. The engraved marks are small and weak, and are partially occluded by ink marks. The whole sense is noisy and has low contrast. A preprocessing for image enhancement is first performed. Then, a simplified numerical correlation algorithm is applied, resulting in a fast and accurate positioning of the marks. The procedure includes designing a model for the target, in a way that greatly reduces the volume of computed data. Three figures of merit are defined to ensure the robustness of the whole procedure: the contrast of the target on the background, the uniqueness of the correlation peak, and the similarity between target and model. By comparison of these figures against suitable threshold levels, decisions based on existence, multiplicity and completeness of the marks can be taken.

Citation Download Citation

Xavier Fernandez and Salvador Bosch "Automatic visual inspection of centering marks engraved on ophthalmic lenses", Proc. SPIE 2249, Automated 3D and 2D Vision, (23 November 1994); https://doi.org/10.1117/12.196113

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